This invention relates generally to handling a flowing mixture, and more specifically to progressive separation of a slug flow into constituent parts within closed pipelines based at least in part on the principles of buoyancy and gravity.
In the field of oil production and transmission, flows of two-phase mixtures (e.g., gas-liquid mixtures) (hereinafter referred to as “two-phase flows”) or other mixtures of constituent parts having varying densities (e.g., liquid-liquid mixtures, gas-liquid mixtures, gas-gas mixtures) (hereinafter referred to as “mixture flows”) are commonly encountered. This is especially true in production carrier pipelines conveying oil mixtures from a producing well. Producing wells, for example, may contain a mixture of oil, water and various gases that are extracted as a mixture flow through a pipeline. These flows must be received by oil handling systems and separated into constituent or component parts based on phase or density for treatment and subsequent distribution to end users.
It is often desirable for flow separation of a mixture to occur prior to the transmission thereof through significant lengths of pipelines. Early mixture flow separation enables mechanical devices functioning within oil production and transmission systems to manage component flows each having substantially only one phase or range of densities. Examples of such mechanical devices include compressors utilized for compressing materials in gaseous states and pumps for moving the flow of liquids. By managing component flow of a single phase or density range, these mechanical devices can be engineered for optimum performance while reducing stresses placed on respective oil handling systems.
Mixture flow separation, however, is not without its difficulties. First of all, many producing wells are positioned at remote locations and in harsh environments, such as on a deep sea floor. In those situations, achieving separate component part flows shortly after the corresponding mixture flow (which may, for instance, include a two-phase flow) leaves the well requires a separation system to be located where it is not easy to install nor easy to access when system maintenance is needed. Further, most conventional systems that achieve efficient component separation may be quite bulky and heavy, reducing the desirability of using such separation systems on overseas platforms where weight and space considerations are a high priority.
One separation system design involves the use of a centrifugal force separator: essentially a curved pathway in a transmission or carrier line with one or more radial ports or annular channels. When a mixture flow achieves a sufficient velocity, centrifugal force will move the denser component (e.g., liquid) to the outside of the curve and into the ports or channels that carry the liquid into a storage container. While this design achieves a certain degree of separation for some mixture flows, it is not very effective for mixtures in the form of slug flows. Slug flow refers to an uneven distribution of components in a mixture flow that creates undesirable cyclic flow characteristics for the mixture. Due to slug flow, surges of components of the flowing mixture (e.g., gas or liquid) may be realized at any given point along the transmission pipeline, impeding efficient mixture flow and causing increase stresses on mechanical devices of the transmission system. Because the mixture flow components often do not arrive at various points in transmission at the same time, centrifugal force separators have a difficult time properly segregating the mixture flow components from one another. Thus, the prior art has not provided a solution for separating mixture flows into constituent parts in a simple and effective manner.